Origin-destination weighted choice model as a new tool for assessing the impact of new urban developments

Different measures of pace syntax analysis have consistently produced efficient representations of urban phenomena, such as movement, which could be used in urban design, urban planning and decision making processes. All these measures, however, are based on pure spatial configurations and are not directly influenced by other attributes of the urban network, such as land use and density. In the absence of data on these attributes, or when the main focus of the study is the spatial layout, the pure spatial analysis remains a very powerful tool, but in cases that we need to study and model the non-spatial attributes of urban areas, it is important to develop methods that could link those attributes intrinsically with the spatial analysis. One of the cases that demands for such methods is the assessment of the impact that large-scale developments create in the city. In this assessment issues such as the different types of uses and their distributions become as important as the spatial layout itself. This paper proposes and tests a methodology to create a space syntax model that could takes into account urban attributes such as land use and density inside the process of spatial analysis. In this approach the syntactic measure of 'choice', or 'betweeness centrality' as it is usually called in network science, is calculated by imposing weightings on the origins and destinations of the shortest path in the urban network. The weightings are obtained from the special conditions of each segment and are used for calculating the choice value of all segments located on the shortest routes between all origins and destinations. The model has been tested in the city of Jeddah, Saudi Arabia, to measure the impact of major urban development on the vehicular traffic demands in the centre of the city. Furthermore, the analysis is used to identify the vulnerabilities of the network in Jeddah after the implementation of the new developments. The paper focuses mainly on the methodological aspects of this approach, which will need further research to generate a consolidated impact assessment methodology for cities.